Family MYCTOPHIDAE

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Lanternfishes are the most widely distributed, diverse and abundant fishes in the deep ocean midwaters.

They are small to medium-sized silvery or black fishes with external light organs or photophores on the head and body, usually in a non-linear series, a moderate to large eye, a jaw that reaches to or beyond the posterior margin of the eye, small teeth (never fang-like), scales, a short to moderate-sized body, an adipose fin and abdominal pelvic fins.

Most lanternfishes undertake daily vertical migrations from daytime depths of 150-2000 m, to feed in shallower waters at night. They comprise more than half of all deep-sea biomass, and are a critical component of marine ecosystems worldwide.

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Family Taxonomy

A large family with more than 250 species in 32 genera. While the described Australian fauna totals an estimated 130 species in 28 genera (John Paxton, pers. comm.), 111 species are included here. The remaining species will be included in a key to the Myctophidae of Australia's maritime waters. The manuscript is being prepared by John Paxton and Alan Williams, and will be published in 2013.

Family Distribution

Found worldwide in all oceans and seas from Arctic to Antarctic waters. Most species are meso- and bathypelagic by day, living at 150-2000 m, migrating vertically to feed in shallower waters at night. Some species even reach surface waters. A few species are benthopelagic over the outer shelves and/or slopes as adults.

Family Description

Body slightly compressed, elongate, eye large, diameter usually much greater than snout length; mouth large, usually terminal jaws moderate to large with bands of small, simple, closely set teeth; maxilla excluded from gape of mouth by premaxilla. Single dorsal over or in front of anal fin, pelvic fins abdominal, pectoral fins absent, or small to large, dorsal adipose fin present. and light organs or photophores arranged in groups and rows on head and body; scales usually cycloid, deciduous. Photophores and other luminous tissue present in most; conspicuous photophores in paired rows or groups on head and body, primary row on ventral surface with smaller groups between ventral row and lateral line; other luminous tissue may include secondary photophores on head and body, specialized photophores on head around eyes, luminous patches or scales at fin bases and luminous organs on caudal peduncle (often in sexually dimorphic patterns).

Family Size

One species reaches 30 cm SL, although most grow to less than 12.5 cm SL; one very small species matures at 3 cm SL.

Carnivores feeding on small planktonic crustaceans, fishes and rarely pelagic molluscs; one species is known to feed on phytoplankton. Lanternfishes are the most important food source in mesopelagic waters, and are preyed upon by many fishes such as tunas, dolphinfish, hakes among others, marine mammals (seals, dolphins, whales) and even seabirds, especially penguins.

Family Reproduction

Lanternfishes are oviparous with pelagic eggs and larvae which drift in the upper layers of the ocean. While the eggs are poorly known for most species, larval lanternfishes are often among the most abundant larvae in plankton samples and are well-known for many species. Eggs small, 0.7-0.9 mm in diameter, yolk segmented, oil globule large and perivitelline space moderately large. Larvae hatch at 2 mm and metamorphose, depending on the species, between 10 to 30 mm. Larval identification to genus and species is based on a large number of characters, such as head, eye, gut and body shape, fin development and meristics, photophore development and placement, and melanophore patterns.Myctophid bioluminescence is intrinsic - produced by a chemical reaction within the body cells. The bioluminescence along the ventral surface of the body plays a role in countershading, or camouflaging the fish from predators by breaking up its silhouette. Each species has a unique photophore pattern which may also be involved in species recognition.

Family Commercial

Lanternfishes have an enormous biomass, comprising 65% of all mesopelagic fishes and represent a potential fishery resource; only a few species are commercially fished off South Africa and in subantarctic waters and are reduced to fishmeal and fish oil.They are also the most important food source in mesopelagic waters, and are preyed upon by many commercially important fishes, such as tunas, hakes and dolphinfish.

Family Remarks

All myctophids have well-developed eyes, and may use their light organs for recognising members of the same species, to signal to members of the opposite sex, and for counter-illumination to camouflage themselves from both predators and prey.

Author

Dianne J. Bray & John R. Paxton

References

Becker, V E. & Y.N. Shcherbachev. 1990. Benthopelagic species of the families Neoscopelidae and Myctophidae from the Indian Ocean, with a description of a new species of Diaphus. Voprosy Ikhtiol. 30(5): 845-855. [In Russian. English transl. in J. Ichthyol. 30(7): 122-134.